Ink-jet inks typically comprise an ink vehicle and a colorant, the latter of which may be a dye or a pigment. Dye-based ink-jet inks used in photographic image printing are usually water-soluble dyes. As a result, such dye-based ink-jet inks are usually not very water fast, i.e. images tend to shift in hue and edge sharpness is reduced upon exposure to humid conditions, especially when printed on media substrates having a porous ink-receiving coating. In addition, images created from these water-soluble dye-based ink-jet inks tend to fade over time, such as when exposed to ambient light and/or air. Pigment-based inks on the other hand, allow the creation of images that are vastly improved in humid fastness and image fade resistance. Pigment based images, however, are inferior to dye-based ink-jet inks with respect to the desirable trait of color saturation and penetration of colorant below a coating surface.
Print media surfaces play a key role in fade properties, humid fastness, and the quality of ink-jet produced printed images. Thus, for a given ink, the degree of air fade, humid fastness, haze, and image quality in general can be dependent on the chemistry of the media surface. As a result, many ink-jet inks can be made to perform better when an appropriate media surface is used.
There are benefits of treating silica or other particulates with cationic agents in connection with ink-jet coatings. However, increasing the level of these cationic agents can also result in a decreased porosity, increased haze, lower gamut, and precipitation of ink dye or pigments on the surface of the media, often resulting in poor smudging and poor color properties.